In recent years, allowing production of images more easily and less expensively than a gravure printing method, the inkjet recording method is applied to various fields of printing including photographing, various printing, special printing such as marking and color filtering. Particularly, inkjet recording allows it to obtain an image quality comparable to a silver halide photograph by a combination of an inkjet printer with an inkjet recording method that jets and controls fine dots, inks having an improved color reproduction area, durability, jettability, etc., and a dedicated paper with a significantly improved ink absorbency, color developability of a color material, surface gloss, etc.
There are known inkjet printers such as a line type which performs image recording by jetting ink from line-heads formed with a plurality of jetting nozzles disposed in the scan direction (recording direction) orthogonal to a conveying direction on a recording medium conveyed in the conveying direction, and a serial type which performs image recording by jetting ink from jetting nozzles of recording heads while moving the recording heads mounted on a carriage in the scan direction (recording direction).
Further, inkjet printers can be categorized by types of ink. That is, there are known inkjet printers such as a phase change inkjet type using wax inks in a solid state at a room temperature, a solvent inkjet type using inks based on a quick drying organic solvent, a UV curing inkjet type using UV curable inks which are cured by irradiating UV light, and so on. Particularly, a UV curing inkjet type makes less smell compared with other recording types, and are paid attention to because it allows recording on a recording medium which is not quick drying or ink absorbent, in addition to dedicated papers (for example, see Patent Document 1).
Further, in recent years, an inkjet printer of a serial type, as described above, jets ink from recording heads not only while a carriage is moving in one direction, namely, a scanning direction, but also while the carriage is moving in the back direction opposite to the scanning direction, which achieves image recording at a high speed.
Incidentally, to form a color image by an inkjet printer, inks in plural colors are jetted superimposedly onto a recording medium to express a special color. However, in the case where ink is jetted during both forward moving and backward moving of a carriage in an inkjet printer of a serial type as described above, the jetting order is reversed by the moving direction, namely forward moving and backward moving of the carriage. Accordingly, even when inks in plurality of colors are jetted in the same combination and amount, a problem occurs in that the color looks different depending on whether the inks are jetted during forward motion or the backward motion.
Therefore, there have been offered inkjet printers in which plural recording heads mounted on a carriage are disposed such that the colors of inks are symmetric so that the jetting order is not changed by forward motion and backward motion (for example, see Patent Document 2).
Further, for an inkjet printer using drainage inks, there have been offered methods which change the ink jetting amount with the moving direction, namely, the forward motion or the backward motion of the carriage, correspondingly to the degree of penetration of ink into a recording medium (for example, see Patent Document 3).
[Patent Document 1] TOKKAI No. 2001-310454
[Patent Document 2] U.S. Pat. No. 3,248,704
[Patent Document 3] TOKKAI No. 2003-25613
However, in accordance with Patent Document 2 described above, the number of recording heads are approximately double that of a printer which jets ink only during forward motion, which forces a printer to have a larger size.
In the case of drainage inks as described in Patent Document 3, since ink penetrates into a recording medium, even when an ink in a different color is jetted superimposed over an ink having been jetted, it is possible to calculate a proper ink amount, taking the relationship between the ink and the recording medium into account. In the case of photo-curable ink, since ink does not penetrate into a recording medium, when jetting an ink in a different color onto an ink having been jetted, not only the relationship between the ink and the recording medium, but also the relationship between the ink to be jetted and the ink having been jetted, landed on the recording medium, and got photo-cured is needed to be taken into account, which has not been considered before. Therefore, the technology disclosed in Patent Document 3 cannot be applied to an inkjet printer using photo-curable ink.